This invention relates to an image reproducing apparatus for displaying a still picture that has been received.
HDTV (high-definition television) has a large number of scanning lines and presents a very fine picture, thus making it possible to fully enjoy not only a moving picture but also a still picture. For this reason, use thereof in the fields of the arts, culture and animation is expected. In case of a still picture, the viewer observes a single picture thoroughly for several seconds to several tens of seconds, and therefore picture quality equivalent to that at the studio is required. Besides an HDTV moving-picture display apparatus, an HDTV still-picture reproducing apparatus has been considered that makes it possible to enjoy still pictures of studio quality.
FIG. 2 illustrates a still-picture reproducing apparatus according to the prior art.
A given information is received by the antenna of a receiver 201 so as to be converted into still-picture information. The output of still-picture information from the receiver 201 is restored to the original still-picture picture data by a still-picture decoder 202, and the still-picture data is developed as a still picture in one of frame memories 203 under the control of a frame memory controller 204. The still picture is read from the frame memory 203 by raster scanning performed by the frame memory controller 204. The read picture data is converted into an analog signal by a D/A converter 205 and is displayed as a still picture on a monitor 206.
The data format of a received still-picture broadcast is illustrated in FIG. 3.
As shown in FIG. 3, the still-picture data comprises data which sets a time that serves as a reference for displaying the condition of the still picture, display-setting data which sets the form in which the picture data is to be displayed, write-setting data for setting in which frame memory picture data is to be stored, and one frame of still-picture data, which is the actual condition of the still picture. A program effect using still-picture data can be considered as one form of display that can be established by the display-setting data. In the program effect, when it is desired to end the display of one still picture and display a still picture of interest, the display on the screen is gradually updated to the still picture of interest (by dissolving, wiping or scrolling) rather than merely changing over the screen. Alternatively, the display on the screen is combined with all (or a part) of an already received still picture in a frame memory.
As set forth earlier, since a still picture of this kind is highly attractive, naturally there are cases where it is desired to display a certain picture continuously. In order achieve this, it has been contemplated to provide the image-reproducing apparatus with a function for "freezing" the picture being displayed and with a function for cancelling the freeze mode. The term "freeze" means that the processing for reading a still picture of interest, which has been developed in a frame memory, from the frame memory to the monitor is continued until a cancel command is entered, and that the writing of other data into the frame memory whose picture is currently being displayed is prohibited.
Certain problems arise when an image reproducing apparatus is provided with such a freeze function. Specifically, in response to cancellation of the freeze mode, the frame memory whose picture is to be displayed is changed over. However, if the new frame memory whose picture is to be displayed is still receiving its data and undergoing writing, the possibility arises that an incomplete picture will be displayed on the screen because the data thereof is still in the process of being written in the frame memory. Such a display is unnatural and can confuse the viewer.
Another problem arises in the case of processing where one's own still picture is to be displayed superimposed on the still picture that has been stored in a frame memory. If this designated frame memory is one whose still picture has been frozen and, hence, the corresponding still picture (the one on which one's own picture is to be superimposed) has not been written therein, the combined picture displayed will be entirely different from the combined picture intended. This can only confuse the viewer.